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3 (C) 2012 Christian Grothoff (and other contributing authors)
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23 * @brief implementation of the invertible bloom filter
24 * @author Florian Dold
30 * Compute the key's hash from the key.
31 * Redefine to use a different hash function.
33 #define IBF_KEY_HASH_VAL(k) (GNUNET_CRYPTO_crc32_n (&(k), sizeof (struct IBF_KeyHash)))
36 * Create a key from a hashcode.
38 * @param hash the hashcode
42 ibf_key_from_hashcode (const struct GNUNET_HashCode *hash)
44 /* FIXME: endianess */
45 return *(struct IBF_Key *) hash;
49 * Create a hashcode from a key, by replicating the key
50 * until the hascode is filled
53 * @param dst hashcode to store the result in
56 ibf_hashcode_from_key (struct IBF_Key key, struct GNUNET_HashCode *dst)
60 const unsigned int keys_per_hashcode = sizeof (struct GNUNET_HashCode) / sizeof (struct IBF_Key);
61 p = (struct IBF_Key *) dst;
62 for (i = 0; i < keys_per_hashcode; i++)
68 * Create an invertible bloom filter.
70 * @param size number of IBF buckets
71 * @param hash_num number of buckets one element is hashed in
72 * @return the newly created invertible bloom filter
74 struct InvertibleBloomFilter *
75 ibf_create (uint32_t size, uint8_t hash_num)
77 struct InvertibleBloomFilter *ibf;
79 /* TODO: use malloc_large */
81 ibf = GNUNET_malloc (sizeof (struct InvertibleBloomFilter));
82 ibf->count = GNUNET_malloc (size * sizeof (uint8_t));
83 ibf->key_sum = GNUNET_malloc (size * sizeof (struct IBF_Key));
84 ibf->key_hash_sum = GNUNET_malloc (size * sizeof (struct IBF_KeyHash));
86 ibf->hash_num = hash_num;
92 * Store unique bucket indices for the specified key in dst.
95 ibf_get_indices (const struct InvertibleBloomFilter *ibf,
96 struct IBF_Key key, int *dst)
102 bucket = GNUNET_CRYPTO_crc32_n (&key, sizeof key);
103 for (i = 0, filled=0; filled < ibf->hash_num; i++)
107 for (j = 0; j < filled; j++)
108 if (dst[j] == bucket)
110 dst[filled++] = bucket % ibf->size;
112 x = ((uint64_t) bucket << 32) | i;
113 bucket = GNUNET_CRYPTO_crc32_n (&x, sizeof x);
119 ibf_insert_into (struct InvertibleBloomFilter *ibf,
121 const int *buckets, int side)
125 for (i = 0; i < ibf->hash_num; i++)
127 const int bucket = buckets[i];
128 ibf->count[bucket].count_val += side;
129 ibf->key_sum[bucket].key_val ^= key.key_val;
130 ibf->key_hash_sum[bucket].key_hash_val
131 ^= IBF_KEY_HASH_VAL (key);
137 * Insert a key into an IBF.
140 * @param key the element's hash code
143 ibf_insert (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
145 int buckets[ibf->hash_num];
146 GNUNET_assert (ibf->hash_num <= ibf->size);
147 ibf_get_indices (ibf, key, buckets);
148 ibf_insert_into (ibf, key, buckets, 1);
153 * Remove a key from an IBF.
156 * @param key the element's hash code
159 ibf_remove (struct InvertibleBloomFilter *ibf, struct IBF_Key key)
161 int buckets[ibf->hash_num];
162 GNUNET_assert (ibf->hash_num <= ibf->size);
163 ibf_get_indices (ibf, key, buckets);
164 ibf_insert_into (ibf, key, buckets, -1);
169 * Test is the IBF is empty, i.e. all counts, keys and key hashes are zero.
172 ibf_is_empty (struct InvertibleBloomFilter *ibf)
175 for (i = 0; i < ibf->size; i++)
177 if (0 != ibf->count[i].count_val)
179 if (0 != ibf->key_hash_sum[i].key_hash_val)
181 if (0 != ibf->key_sum[i].key_val)
189 * Decode and remove an element from the IBF, if possible.
191 * @param ibf the invertible bloom filter to decode
192 * @param ret_side sign of the cell's count where the decoded element came from.
193 * A negative sign indicates that the element was recovered
194 * resides in an IBF that was previously subtracted from.
195 * @param ret_id receives the hash code of the decoded element, if successful
196 * @return GNUNET_YES if decoding an element was successful,
197 * GNUNET_NO if the IBF is empty,
198 * GNUNET_SYSERR if the decoding has failed
201 ibf_decode (struct InvertibleBloomFilter *ibf,
202 int *ret_side, struct IBF_Key *ret_id)
204 struct IBF_KeyHash hash;
206 int buckets[ibf->hash_num];
208 GNUNET_assert (NULL != ibf);
210 for (i = 0; i < ibf->size; i++)
215 /* we can only decode from pure buckets */
216 if ((1 != ibf->count[i].count_val) && (-1 != ibf->count[i].count_val))
219 hash.key_hash_val = IBF_KEY_HASH_VAL (ibf->key_sum[i]);
221 /* test if the hash matches the key */
222 if (hash.key_hash_val != ibf->key_hash_sum[i].key_hash_val)
225 /* test if key in bucket hits its own location,
226 * if not, the key hash was subject to collision */
228 ibf_get_indices (ibf, ibf->key_sum[i], buckets);
229 for (j = 0; j < ibf->hash_num; j++)
233 if (GNUNET_NO == hit)
236 if (NULL != ret_side)
237 *ret_side = ibf->count[i].count_val;
239 *ret_id = ibf->key_sum[i];
241 /* insert on the opposite side, effectively removing the element */
242 ibf_insert_into (ibf, ibf->key_sum[i], buckets, -ibf->count[i].count_val);
247 if (GNUNET_YES == ibf_is_empty (ibf))
249 return GNUNET_SYSERR;
254 * Write buckets from an ibf to a buffer.
255 * Exactly (IBF_BUCKET_SIZE*ibf->size) bytes are written to buf.
257 * @param ibf the ibf to write
258 * @param start with which bucket to start
259 * @param count how many buckets to write
260 * @param buf buffer to write the data to
263 ibf_write_slice (const struct InvertibleBloomFilter *ibf, uint32_t start, uint32_t count, void *buf)
265 struct IBF_Key *key_dst;
266 struct IBF_KeyHash *key_hash_dst;
267 struct IBF_Count *count_dst;
269 GNUNET_assert (start + count <= ibf->size);
272 key_dst = (struct IBF_Key *) buf;
273 memcpy (key_dst, ibf->key_sum + start, count * sizeof *key_dst);
275 /* copy key hashes */
276 key_hash_dst = (struct IBF_KeyHash *) key_dst;
277 memcpy (key_hash_dst, ibf->key_hash_sum + start, count * sizeof *key_hash_dst);
278 key_hash_dst += count;
280 count_dst = (struct IBF_Count *) key_hash_dst;
281 memcpy (count_dst, ibf->count + start, count * sizeof *count_dst);
286 * Read buckets from a buffer into an ibf.
288 * @param buf pointer to the buffer to read from
289 * @param start which bucket to start at
290 * @param count how many buckets to read
291 * @param ibf the ibf to read from
294 ibf_read_slice (const void *buf, uint32_t start, uint32_t count, struct InvertibleBloomFilter *ibf)
296 struct IBF_Key *key_src;
297 struct IBF_KeyHash *key_hash_src;
298 struct IBF_Count *count_src;
300 GNUNET_assert (count > 0);
301 GNUNET_assert (start + count <= ibf->size);
304 key_src = (struct IBF_Key *) buf;
305 memcpy (ibf->key_sum + start, key_src, count * sizeof *key_src);
307 /* copy key hashes */
308 key_hash_src = (struct IBF_KeyHash *) key_src;
309 memcpy (ibf->key_hash_sum + start, key_hash_src, count * sizeof *key_hash_src);
310 key_hash_src += count;
312 count_src = (struct IBF_Count *) key_hash_src;
313 memcpy (ibf->count + start, count_src, count * sizeof *count_src);
318 * Subtract ibf2 from ibf1, storing the result in ibf1.
319 * The two IBF's must have the same parameters size and hash_num.
321 * @param ibf1 IBF that is subtracted from
322 * @param ibf2 IBF that will be subtracted from ibf1
325 ibf_subtract (struct InvertibleBloomFilter *ibf1, const struct InvertibleBloomFilter *ibf2)
329 GNUNET_assert (ibf1->size == ibf2->size);
330 GNUNET_assert (ibf1->hash_num == ibf2->hash_num);
332 for (i = 0; i < ibf1->size; i++)
334 ibf1->count[i].count_val -= ibf2->count[i].count_val;
335 ibf1->key_hash_sum[i].key_hash_val ^= ibf2->key_hash_sum[i].key_hash_val;
336 ibf1->key_sum[i].key_val ^= ibf2->key_sum[i].key_val;
342 * Create a copy of an IBF, the copy has to be destroyed properly.
344 * @param ibf the IBF to copy
346 struct InvertibleBloomFilter *
347 ibf_dup (const struct InvertibleBloomFilter *ibf)
349 struct InvertibleBloomFilter *copy;
350 copy = GNUNET_malloc (sizeof *copy);
351 copy->hash_num = ibf->hash_num;
352 copy->size = ibf->size;
353 copy->key_hash_sum = GNUNET_memdup (ibf->key_hash_sum, ibf->size * sizeof (struct IBF_KeyHash));
354 copy->key_sum = GNUNET_memdup (ibf->key_sum, ibf->size * sizeof (struct IBF_Key));
355 copy->count = GNUNET_memdup (ibf->count, ibf->size * sizeof (struct IBF_Count));
361 * Destroy all resources associated with the invertible bloom filter.
362 * No more ibf_*-functions may be called on ibf after calling destroy.
364 * @param ibf the intertible bloom filter to destroy
367 ibf_destroy (struct InvertibleBloomFilter *ibf)
369 GNUNET_free (ibf->key_sum);
370 GNUNET_free (ibf->key_hash_sum);
371 GNUNET_free (ibf->count);